Onsite power generation has become increasingly popular. For decades now, particularly in areas that are prone to power outages and/or for businesses that require uninterrupted power, oil and diesel backup power systems have been used to generate onsite power when the grid is unavailable. These systems generate alternating current (AC) power that ties into a customer's existing power distribution system, typically on the load side (i.e., between the utility meter and the main panel) or directly into the main customer panel. More recently, continuous onsite generation based on alternative energy sources has increased in popularity.
Like back-up power systems, onsite alternative energy generating systems are frequently retrofit into existing structures which may have electrical systems that are not by default setup to accept additional energy inputs. One solution to this has been to wire directly to the bus bars of the customer's main electrical panel. However, this solution is not ideal because current national electric code limits the amount of current that can be delivered to the bus bars to 20 percent of the main breaker's capacity. So this in turn will limit the maximum capacity of an onsite power generation system connected in this way.
To deal with this problem, installers of onsite power generation systems frequently have to upgrade the customer's main electrical panel so that it has enough excess current capacity on the bus bars to accommodate the desired generation system. Then the power from the onsite generation system can be fed directly into the main panel and either power the home or business or back feed power to the grid.
Another solution to interfacing to existing grid power at the customer premises has been to utilize a so-called meter socket adapter or MSA. The MSA fits in between the meter socket in the customer's existing main panel and the utility company's meter. Usually the MSA has an opening or input collar to receive the AC output of an onsite power generation system. This is preferable to upgrading the main panel because it requires very little labor and is not affected by the current limitations of the bus bars in the customer's existing main electrical panel. Two such MSAs are disclosed in commonly assigned U.S. Pat. Nos. 8,784,130 and 7,648,389, the disclosures of which are hereby incorporated by reference in their entirety.
In a typical residential or commercial (e.g., 120V/240V) system, the meter itself has only two inputs and two outputs—it does not use the neutral wiring coming in from the utility or flowing out to the customer's main electrical panel—yet the onsite power generation system typically has two AC lines plus a neutral wire. As a result, when interfacing an onsite power generation system to a customer's electrical panel with an MSA, such as that disclosed in U.S. Pat. Nos. 8,784,130 and 7,648,389, the neutral wire has to be run through the MSA, typically through a built in aperture, so that the loose end can be spliced with the grid neutral running through the meter socket. This is less than optimal. First, it requires additional manual wiring to the neutral through the adapter so that the unconnected adapter is dangling while the neutral is being wired. Second, after the wiring has been completed and the adapter connected to the socket, if at any point the adapter has to be removed, simply pulling it out won't disconnect it from the meter socket in the electrical panel because the neutral wire will remain connected and must be manually disconnected.
Therefore, there exists a need for a mechanism for interfacing an onsite power generation system to a customer's power distribution system that ameliorates the shortcomings of conventional solutions.